Quote Originally Posted by 04trbogp View Post
Would a broken coolant elbow cause the service brake system light to appear?
engine overheating puts the pcm into a save the day mode, changing shift points, alternator turn on, fans etc. so yes it could be a byproduct especially if the pcm killed the alternator field and charging voltage dropped the abs/trac/etc would be shutdown.

it could be independently triggered from a brake system fault, but so many things are interconnected on these nowadays id suggest fixing the coolant elbows and retesting